L23 Summary and Conclusions
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This lecture discusses challenges in building enterprise applications and provides advice. It recommends starting simply and evolving designs over time. Complex systems designed from scratch never work, so layering, clear interfaces, and minimizing dependencies are important. Frameworks and design patterns help manage complexity but shouldn't dictate design. Practical considerations include avoiding unnecessary complexity and refactoring when needed.
L23 Summary and Conclusions
- 1. Lecture 23 Summary and Conclusions
- 2. “Advice is a dangerous gift” There are no right answers Use the advice to prod your thinking, but don’t use it as a replacement for your thinking And remember, architecture is not cast in stone
- 3. Building Enterprise Applications Building computer systems is hard – As the complexity of the system gets greater, the task of building the software gets exponentially harder
- 4. Building Enterprise Applications Building computer systems is hard Design Pattern Software Architecture Middleware Frameworks OO Programming
- 5. Building Enterprise Applications Building computer systems is hard But now when we know how to, it’s not that hard anymore
- 6. “A complex system that works is invariably found to have evolved from a simple system that worked. The inverse proposition also appears to be true: a complex system designed from scratch never works and cannot be made to work. You have to start over, beginning with a simple system.” — John Gall, systems theorist
- 7. Goals of an Enterprise Architecture Be robust Be performing and scalable Take advantage of OO design principles Avoid unnecessary complexity Be maintainable and extensible Be easy to test
- 8. Enterprise Systems Building large multi-tier systems is done one line at a time – Layering – Clear interfaces – Minimize dependencies – Separation of concerns – Object Oriented programming – Design patterns – Frameworks – Testable code
- 9. Create Abstractions Minimize dependence on subsystems – Must be easy to change • Gateway, Mapper, Service Stub Abstract things that varies from what stays the same – Design principles • Factory, Plugin, Dependency Injections
- 10. Separation of Concerns One of the main challenge of frameworks is to provide separation of concerns Frameworks deal with generic functionality Frameworks need patterns to combine generic and domain specific functionality
- 11. Minimize dependencies Be careful with dependencies – It is easy to create code where modules depend on other modules • Plugin, Factory, Service Layer, Separated Interface, Dependency Injection and Observer Pattern
- 12. Layering Software systems can get complicated – Abstractions are needed Provides abstraction by separating computer systems in layers – Higher layers use services from lower layers – Each layer has dedicated task and hides complexity from upper layers
- 13. The Three Layers Presentation – User’s interface to the system – User can be another system – Accepts input, displays views Domain – The Application of the system – The “Business logic” – Has the tendency to creep into other layers Data Source – Connection to the database
- 14. Three Layers Presentation Layer for the User Interface Domain Layer for the domain logic Persistence Layer for the data access Remember the “role” – concern, in each layer
- 15. Considerations Don’t overdesign! – User Interfaces are really difficult to make generic and reusable – If there is no need for extra layer, don’t have it – If you don’t need an interface, don’t have it Don’t let frameworks rule you! – If you have to write code just to satisfy a framework, maybe there is another way – or fix the framework – Frameworks can overdo it
- 16. Considerations Don’t overdo Configurations – Sometimes coding is better than config – Testing and debugging config is hard Don’t be afraid to Refactor – You can always add another indirection – You can always add a new layer Design Principles are good guidelines – Don’t be afraid to reevaluate them
- 17. Considerations Embrace new tools and techniques – These exist to help you – But be careful, don’t jump at everything – there is a cost Use Tech Rader to evaluate – Example: ThoughtWorks Radar http://www.thoughtworks.com/radar
- 18. Practical Considerations Risk is in feature creep and things out of control
- 19. Practical Considerations Solutions are designed and implemented according to time schedule and budget – Hardest part is management of people
- 20. Practical Considerations Agile is an attempt to answer this Backlog Backlog ordered by Product Owner Sprint stories Daily Standup 1-2 week sprints Working Product Working Product Released
- 22. Tech Radar
- 23. Tech Radar ADOPT Start using when appropriate TRIAL Learn and try out to understand ASSESS Evaluate how this will impact the company HOLD Proceed with causion
- 24. Trends 2014 Churn in the JavaScript World – Rise of JavaScript libraries Microservices and the Rise of the API – Importance of the APIs both within an organization and as a bridge to the outside world Conway's Law – Ignoring this law is dangerous Re-decentralization – Data and infrastructure
- 29. Future of Enterprise Software
- 30. THE DIGITAL DECADE MUSIC PICTURE S TV SHOWS MOVIES 2000 2010 VOICE SMARTPHONES BOOKS
- 31. Mainframes Mini computers DIVERGE Personal Computers Servers Laptops 2G Cell phones Clusters Smartphones Tablets Smart TV Wearable Cloud – utility computing Music player CONVERGE 1960 1970 1980 1990 2000 2010 Internet of things SaaS - APIs
- 32. Wearable Era
- 34. Digital Online World Work More information Focused Browsing Consuming content Checking Mobile Now Consuming Video Information Real-time
- 35. The Post-PC Era The Personal Computer era is over – Rise of the network – APIs – Enterprise systems are accessible by consumers – New devices, mobile phone, ITV, game machines, MP3 players,... Source: (cc) 1998-2008 Digibarn Computer Museum, Source: Picture from Convergence Transforms Digital Home: Techno-Economic Impact
- 36. Challenges in Computing Hardware Connecting hardware Network Software 1980 1990 2000 Connecting software Software and integration of components and devices are the challenges ahead Cloud computing and ubiquity Move to Service Oriented Architecture and APIs
- 37. Challenges in Computing Software Connecting software Mobility Wearables APIs, SaaS, real-time 2000 2010 2020 Multiple devices – anything can connect Ability to predict – know the users Data Analytics aka Big Data Real-time streams
- 38. Hönnun og smíði hugbúnaðar 2014
- 39. Objectives Know the basics of software design and beautiful code Understand and know how to use design patterns Implement software framework with component reuse in mind
- 40. Objectives continued Understand different software architectures and the different design choices Understand Software Oriented Architecture (SOA) and Software as a Service (SaaS) Understand the practices of how professional software is developed in the software industry
- 43. Næst Síðasti tími fyrir próf